Thermolytic digest of chicken pepsin

Abstract

Chicken pepsin prepared by the activation of pepsinogen was digested with thermolysin. The thermolytic digest was fractionated by chromatography on Sephadex G-25 fine. Certain fractions were subsequently subjected to ion exchangechromatography on Dowex 50-X2. The final purification was effected by paper chromatography and high voltage electrophoresis. By these procedures a series of homogeneous peptides was obtained; of the latter 54 nonoverlapping (save for a few exceptions) peptides are described in this paper. These peptides in addition to the thermolytic peptides reported before represent 80% of the linear structure of the whole molecule. The N-terminal amino acid sequence of chicken pepsin is discussed from the viewpoint of the recent data obtained by the analysis of the thermolytic digest.